SB 4.19.34

māsmin mahārāja kṛthāḥ sma cintāṁ
 niśāmayāsmad-vaca ādṛtātmā
yad dhyāyato daiva-hataṁ nu kartuṁ
 mano ’tiruṣṭaṁ viśate tamo ’ndham
Synonyms: 
— do not; asmin — in this; mahā-rāja — O King; kṛthāḥ — do; sma — as done in the past; cintām — agitation of the mind; niśāmaya — please consider; asmat — my; vacaḥ — words; ādṛta-ātmā — being very respectful; yat — because; dhyāyataḥ — of him who is contemplating; daiva-hatam — that which is thwarted by providence; nu — certainly; kartum — to do; manaḥ — the mind; ati-ruṣṭam — very angry; viśate — enters; tamaḥ — darkness; andham — dense.
Translation: 
My dear King, do not be agitated and anxious because your sacrifices have not been properly executed due to providential impediments. Kindly take my words with great respect. We should always remember that if something happens by providential arrangement, we should not be very sorry. The more we try to rectify such reversals, the more we enter into the darkest region of materialistic thought.
Purport: 

Sometimes the saintly or very religious person also has to meet with reversals in life. Such incidents should be taken as providential. Although there may be sufficient cause for being unhappy, one should avoid counteracting such reversals, for the more we become implicated in rectifying such reversals, the more we enter into the darkest regions of material anxiety. Lord Kṛṣṇa has also advised us in this connection: we should tolerate things instead of becoming agitated.